Typically, a computer system includes a number of integrated circuit chips that communicate with one another to perform system applications. Often, the computer system includes a controller, such, as a micro-processor, and one or more memory chips, such as random access memory (RAM) chips. The RAM chips can be any suitable type of RAM, such as dynamic RAM (DRAM), double data rate synchronous DRAM (DDR-SDRAM), graphics DDR-SDRAM (GDDR-SDRAM), and pseudo static RAM (PSRAM). The controller and RAM communicate data with one another to perform system applications.
Some computer systems include mobile applications and have limited space and limited power resources. In mobile applications, such as cellular telephones and personal digital assistants (PDAs), memory cell density and power consumption are issues for future generations. To address these issues, the industry is developing RAM for mobile applications. One type of RAM, referred to as CellularRAM, is a high performance and low power memory designed to meet memory density and bandwidth demands of future generations. CellularRAM is a PSRAM that offers static RAM (SRAM) pin and function compatibility, external refresh-free operation, and a low power design. CellularRAM devices are drop-in replacements for most asynchronous low power SRAMs used in mobile applications, such as cellular telephones. Typically, a PSRAM is based on a DRAM that provides significant advantages in density and speed over traditional SRAM.
As chip speeds continue to increase, the amount of data communicated between chips continues to increase to meet the demands of system applications. Typically data is received at an integrated circuit, such as a RAM, and sampled via a strobe signal that is also received at the integrated circuit. Higher bandwidth communication links can be built by increasing input/output (I/O) data bit and strobe signal speeds. However, increasing I/O data bit and strobe signal speeds can lead to problems with signal skew through the receivers of the integrated circuit.
The rising edges of the data and strobe signals propagate through the receivers at different speeds than the falling edges of the data and strobe signals. Also, process variations, temperature variations, and voltage variations can increase signal skew through the receivers. Skewed data and strobe signals contribute to setup and hold window shifts during sampling of the data and data recovery in the integrated circuit. Improved receiver performance can be attained via more complex designs, but at the cost of circuitry that may not be reliable and an increase in power consumption.
For these and other reasons there is a need for the present invention.